The subject matter disclosed herein generally relates to blade outer air seals in gas turbine engines and, more particularly, to thermal lifting members for blade outer air seal supports.
Rotor tip clearance is essential to turbomachinery efficiency and fuel consumption, particular in gas turbine engines. It is desirable to minimize the clearance between rotating blade tips and static outer shroud seals (e.g., blade outer air seals). This is currently accomplished in gas turbine engines with active clearance control (ACC), which uses cool air to impinge on the case and control thermal expansion, thus keeping the outer shrouds at a smaller diameter and reducing the clearance to the blade. In aerospace applications, ACC is traditionally employed during a cruise portion of flight of an aircraft. A conventional ACC system is governed by the thermal response of the components and the time constant is generally too slow to use in rapid throttle applications. For instance, if a hot reacceleration is performed, there is a danger of excessive rubbing of the blade tip. The rotor would immediately add the mechanical growth of the acceleration to the existing thermal growth of the hot disk, whereas the case structure would not be able to heat up sufficiently quickly to get out of the way. Accordingly, it is desirable to control rotor blade interaction with static outer shroud seals.